The long-term objective of the research is to understand how the emerging multi-drug resistant opportunistic pathogen, Stenotrophomonas maltophilia (formerly known as Pseudomonas maltophilia or Xanthomonas maltophilia), can result in serious infections in immunocompromised patient populations. Infection of these patients with this respiratory pathogen is associated with a significant case-fatality ratio. The proposed specific research aim is to elucidate genes related to biofilm formation of S. maltophilia. Currently little information is available about the genetic mechanisms used by this bacterium for biofilm formation. This ubiquitous bacterium can form bacterial films (biofilms) on the surfaces of medical equipment in hospitals and implanted devices in patients. These biofilms can act as pervasive and persistent sources of nosocomial infections by S. maltophilia. Biofilm infections are notoriously difficult to treat with antimicrobial therapies. The broad drug resistance and biofilm forming ability of S. maltophilia make this a pathogen of significant concern for physicians. Taken together, these observations underscore the need to understand the molecular mechanisms involved in S. maltophilia biofilm formation in order to develop pharmacological strategies to prevent, or at least retard, biofilm formation by S. maltophilia. We hypothesize that biofilm-defective mutants of S. maltophilia can be generated in vivo and that the mutated gene(s) can be recovered and characterized. We will assess the effects of the mutations on the adherence and biofilm formation of these mutants on clinically relevant surfaces, using biofilm assays, gene expression and detection methodologies, electron microscopy, and cell culture assays. The results of these studies will help to uncover the molecular basis of adherence and biofilm formation by S. maltophiliia. The research program defined in this Academic Research Enhancement Award (AREA) proposal will provide an excellent training opportunity for students to gain experience in molecular biology, biochemistry, cell biology, and cell ultrastructure.